Default Theme?

I want 95% of my Frontend Lovelace pages to be assigned to a specific theme, so I did just that - and of course everything changed. But then I want one or two cards to follow the standard HA theme. But that seems impossible since “default” is now according to my modified setting. So changing the theme for a specific card to “default” does absolutely nothing.
How can I change a specific cards theme back to the original HA theme when there is no name for that theme?